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TED Talks about rainbows

18 April 2022 | Story Leonie Bolleurs | Photo Stephen Collett

“A rainbow is a natural phenomenon, the result of the refraction and reflection of the sun’s rays in drops of rain. As far as mankind is concerned, it’s a perfectly useless object and won’t make anyone money. Yet the poet who said, My heart leaps up when I behold a rainbow in the sky, only put into word the feeling of wonder and excitement we all have when we see a rainbow.”

“Every day I see a rainbow in my work; I do not need to wait to see one in the sky,” says Prof Ted Kroon, Professor in the Department of Physics at the University of the Free State (UFS), who used this phenomenon to introduce the topic of his inaugural lecture: What’s the use of a rainbow.

“Far from being only a colourful spectacle with no practical value, rainbows are useful – and lead to useful things,” he believes.

According to Prof Kroon, one can find examples of real rainbows and rainbow analogies used not only in everyday life, but also in physics. “Besides it being familiar devices in literature, culture, and even marketing, studies of rainbows can yield practical engineering information and may even help us to find new habitable planets,” he says.

Inspired by the many uses of a rainbow

In his lecture, he discussed the basic features of natural rainbows and how they come about. He also explored how the rainbow gives meaning to colour, and how this relates to the temperature of objects. He looked at an array of instances where the rainbow is used; from depicting the life of a star to indicating that we are sick (a thermometer) or when we need to refill a gas cylinder.

Moreover, Prof Kroon pointed out that rainbows are used in computer chips, stress identification, and to transmit internet data through underwater cables of glass fibre. He also referred to how the rainbow was harnessed as an engineering tool to measure refractive index and characterise fine droplet sprays used in industry.

He continues, “Remarkably, the science developed to understand the natural rainbow can be redirected and applied to the optical properties of metallic nanoparticles, allowing the development of nanotechnology. Knowing how the natural rainbow works and its limitations, better systems have been developed to produce rainbows. Such rainbows have been used to discover new elements and to determine the age of the universe.”

As a member of an international community of phosphor researchers who are privileged to work with rainbows every day, he has used them to study the light-emitting properties of materials doped with bismuth. With this project – an initiative with the African Laser Centre taking place between 2016 and 2021 – he collaborated with the University of Khartoum in Sudan and trained a number of its postgraduate students. “My role included the guidance of students and the measurement and interpretation of the light-emitting properties of the materials. Our research during this time, considering more than a dozen materials, was summarised in 34 scientific publications that contributed to a greater understanding of bismuth ions as light-emitting materials,” he explains.

Developing new materials, efficient in emitting blue light

He has been developing luminescent materials since 2006, primarily for general lighting (fluorescent tubes and LEDs) and displays (television, computer, and cellphone screens), as well as niche applications in medical and forensic science.

As part of his current research, he is examining the effect of plasmonic metal nanoparticles on phosphor light emission. He is also exploring materials that absorb infrared light but emit visible light. “For this, I would like to consider the long-term stability of such materials and develop new materials that are more efficient in emitting particularly blue light,” he says.

Prof Kroon holds a C2 rating from the National Research Foundation and has published more than 150 articles and book chapters, obtaining a Scopus h-index of 26.

News Archive

Bullying in schools: Everyone’s problem

2005-06-03

From left: Prof Gerhardt de Klerk, Dean: Faculty of the Humanities; Prof Corene de Wet; Prof Rita Niemann, Head of the Department of Comparative Education and Educational Management in the School of Education and Prof Frederick Fourie, Rector and Vice-Chancellor of the UFS

It is not only learners who are the victums of bullying in schools, but also the teachers. Prof. Corene de Wet from the Department Comparative Education and Educational Management at the University of the Free State reported, against the background of two studies on bullying in Free State secondary schools, that bullying is a general phenomena in these schools.

Prof. de Wet, who delivered her inaugural lecture on Wednesday night, is from the Department Comparative Education and Educational Management which resorts under the School of Education at the University of the Free State. She is the first women who became a full professor the School of Education.

Prof. de Wet says, “A student is being bullied or victimized when he or she is exposed, repeatedly and over time, to negative action on the part of one or more students. Bullying always includes the intentional use of aggression, an unbalanced relationship of power between the bully and the victim, and the causing of physical pain and/or emotional misery.

In some Free State schools there are victims and perpetrators of direct and indirect verbal, as well as emotional, physical and sexual bullying.

“Adults who say that bullying are part of the growing-up process and parents who set not only academic expectations but also social expectations to their children cause that victims are unwilling to acknowledge that they are being bulled. Many parents are also unaware of the levels of bullying their children are exposed to.

“Some of the learners were at least once a month the victim of direct verbal harassment, 32,45% were assaulted by co-learners and 11,21% of them were at east once per week beat, kicked, pushed and hurt in any other physical way. Free State learners are very vulnerable to bullies at taxis and on the school yard they are mostly exposed to bullies in bathrooms.

“Learners are usually bullied by members of the same gender. However, racial composition also plays a role in some Free State schools. A grade 12 girl writes, ‘There are boys in my school who act means against black people. When the teacher is out they take a red pen and write on the projector and spray it with spirits. It looks like blood and they would say it is AIDS and my friends and I have it.’

“Educators must take note of bullying in schools and must not shrug it off as unimportant. Principals or educators could be find guilty of negligence. A large number of educator respondents, 88,29%, indicated that they would intervene in cases of verbal bullying and 89,71% would intervene if they saw learners being physically bullied. However, only 19,97% of the learners who were victims of bullying were helped by educators/ other adults from their respective schools.

“The learners’ lack of trust in their educators’ abilities and willingness to assist them in the fight against bullying has important implications for education institutions. The importance of training must be emphasised.

Learners bully their educators to undermine their confidence. In Prof. de Wet’s study on educator-targeted bullying in Free State schools 24,85% of the respondents were physically abused by their learners, 33,44% were the victims of indirect verbal bullying, and 18,1% were at one time or another sexually harassed by their learners. These learner offences may lead to suspension.

“Educators are not only victims of bullying; some of them are the bullies. The South African Council for Educators prohibits bullying by educators. It is worrying that 55,83% of the educators who participated in the research project verbally victimised learners, 50,31% physically assaulted learners and a small percentage was guilty of sexual harassment.

“Every educator and learner in South Africa has the right to life, equal protection and benefit of the law, of dignity, as well as of freedom and security of the person. These rights will only be realised in a bully-free school milieu.

“To oppose bullying a comprehensive anti-bullying programme, collective responsibility and the establishment of a caring culture at schools and in the community is necessary,” said Prof. de Wet.

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